This invention relates generally to a control valve for regulating fluid pressure, and in particular to a variable pressure solenoid control valve.
Modern automotive transmissions typically require precise electro-hydraulic solenoid valves in order to regulate the hydraulic pressure within the various clutches and spool valves typically employed in such transmissions. The types of solenoid valves commonly employed in flow control valves used in automotive transmissions include: on/off solenoid valves, pulse-width-modulated (PWM) solenoid valves, and variable pressure solenoid (VPS) control valves. Historically automotive manufacturers have chosen to use only a single VPS control valve in their flow control valves that acts as a line-pressure regulation valve. However, in an effort to simplify the calibration of the transmissions and improve the shift quality, automotive manufacturers are now choosing to incorporate the use of several VPS control valves; electing to use them not only for line pressure regulation but also for clutch pressurization and depressurization.
Conventional VPS control valves provide a low control pressure by bleeding-off control pressure to an exhaust downstream from a very small upstream orifice. This method suffers from a number of problems. The first problem is excessive leakage. When only a single 2-port bleeding-off style VPS control valve is used in a transmission, the transmission fluid pump is capable of maintaining pressure even with this leakage; however, when several of these VPS control valves are used in a single transmission, the pump is no longer capable of making-up for the leakage. The second problem that is present in the current 2-port bleeding-off style VPS control valves is that the valves are not capable of reducing control pressure to zero in a normally-high pressure configuration.
The present invention is directed to overcoming one or more of the limitations of existing variable pressure solenoid control valves.
According to one embodiment of the invention, a proportional variable pressure solenoid valve for controlling the pressure of a pressurized fluid in a hydraulic system in proportion to the current level of an electrical input signal is provided that includes a movable valve for controlling the pressure of the pressurized fluid in the hydraulic system, a solenoid for controlling the movement of the movable valve, and a common housing. The movable valve includes an inlet valve for controlling the flow of pressurized fluid into the solenoid valve, and an exhaust valve for controlling the exhaust of pressurized fluid from the solenoid valve. The solenoid includes a spring biased armature for displacing the movable valve, and an electromagnetic coil for generating a variable electromagnetic field in response to the electrical input signal for moving the spring biased armature.
According to another embodiment of the invention, a fluid control device for an automotive transmission is provided that includes a pump for generating a pressurized fluid, a spool valve operably coupled to the pump for controllably conveying the pressurized fluid from the pump to another hydraulic device, the spool valve including a pilot port for receiving a control pressure for controlling the operation of the spool valve, and a proportional variable pressure solenoid valve for receiving the pressurized fluid and generating the control pressure for controlling the operation of the spool valve in proportion to the current level of an electrical input signal. The proportional variable pressure solenoid valve includes a movable valve for controlling the pressure of the control pressure in the hydraulic system, a solenoid for controlling the movement of the movable valve, and a common housing. The movable valve includes an inlet valve for controlling the flow of pressurized fluid into the solenoid valve, and an exhaust valve for controlling the exhaust of pressurized fluid from the solenoid valve. The solenoid includes a spring biased armature for displacing the movable valve, and an electromagnetic coil for generating a variable electromagnetic field in response to the electrical input signal for moving the spring biased armature.
According to another embodiment of the invention, a method of operating a variable pressure solenoid control valve for generating a control pressure for controlling the operation of an hydraulic device using a pressurized fluid in an hydraulic system in proportion to the current level of an electrical input signal, the variable pressure control valve including an hydraulic section including a movable valve for controlling the pressure of the control pressure and a magnetic section including a solenoid for controlling the operation of the movable valve, that includes controllably inputting pressurized fluid into the movable valve through a first port, outputting the control pressure from the movable valve through a second port, and controllably exhausting pressurized fluid from the movable valve through a third port.
The present embodiments of the invention provide a number of advantages. For example the variable pressure solenoid control valves control the pressure of a pressurized fluid in a hydraulic system in proportion to the current level of an electrical input signal by using a 3-port movable valve that includes an inlet ball valve and an exhaust ball valve. In this manner, the control pressure provided by the variable pressure solenoid control valves can be reduced to zero in a normally high pressure or normally low pressure configuration. Moreover, in the normally high and low pressure configurations, when the control pressure is reduced to zero there is no leakage, and in the normally low pressure configuration, when the control pressure is a maximum, the leakage is minimized. Thus, the present embodiments of the invention provide variable pressure solenoid control valves having increased efficiency and improved operational performance.